If you’ve spent much time around the local gun range, chances are good that the terms “double action” and “single action” will not be new to you. In fact, even if you haven’t spent much time at the range (yet), and have just received your RPAL, you probably remember the instructor or examiner asking you to demonstrate how to safely handle either a single action or double action pistol. But although you might have known how to safely unload and open either, there are quite a few folks out there that haven’t quite wrapped their head around just what those particular terms refer to, and what they actually mean. If that sounds like you, read on… we won’t judge.
First off, it’s important to recognize that there is a certain hierarchy of pistol classification, and the broadest rung of that classification hierarchy is the definition of whether or not the pistol in question is a revolver or a semi-automatic. Now, it’s a step that’s certainly obvious to most, but it leads to the first stumbling block that some folks face when it comes to understanding the difference between single and double action pistols… but more on that later.
Obviously, a revolver is pretty easy to spot. There’ll be the usual arrangement of a barrel and a grip, and in between the two will be a nice round magazine, which in the case of a revolver, is referred to as simply a cylinder. A semi-automatic, by comparison, looks thoroughly modern, and is conspicuously flat by comparison. Instead of the cylinder joining the grip with the barrel, the entire frame of the pistol will often be formed from a single piece, with the barrel itself typically residing underneath a slide of some sort and only visible at the muzzle and through the hole on the slide that forms the pistol’s ejection port. The magazine, always removable, is typically located inside the grip itself and is released via either a button on the grip or a lever on the bottom of the trigger guard.
Now it’s time to discuss what single and double action denote. Although it might seem complicated, at their most basic, these terms describe how many actions the trigger can accomplish on its own. In the case of a single action pistol, the trigger can do just one thing: release the hammer. This means of course, that since squeezing the trigger can only release the hammer, the hammer must first be cocked if the gun is to fire. Otherwise, the trigger does nothing. This, the single action pistol, is a far simpler design to engineer and manufacture and subsequently categorizes the majority of pistol designs used into the 19th century.
Which brings us to the double action. Developed in 1851 by a British arms designer named Roberts Adams, who was working for London-based gunmaker George & John Deane, the first double action revolver debuted as a cap-and-ball (denoting the use of percussion caps to ignite the powder charge and fire a lead ball rather than a bullet), five-shot revolver chambered in .436 Dean and Adams. Differing dramatically from any other handgun available at the time, the Dean and Adams revolver had no hammer spur with which the gun could be cocked, and in fact could not be cocked before firing. Instead, as the trigger was pulled, an internal mechanism cocked the hammer rearward and released it, firing the gun. Since the trigger now completed both the task of cocking, and releasing the hammer, the term double action was applied. Four years later, a Lieutenant Frederick E.B. Beaumont would improve the design by allowing the gun to be cocking manually before firing, allowing it to be operated as either a single and double action pistol. This design would become the basis for nearly every double action revolver to come.
Of course, it’s easy enough to understand how the terms single action and double action are applied to revolvers, as the mechanism is both visibly exposed and manually operated. But how does all this work in relation to the semi-automatic, or to use the older colloquialism, automatic handgun? Well, in precisely the same way. On a single-action semi-automatic like Colt’s Model 1911, the trigger is still only capable of one thing; releasing the hammer. So, for that first shot, the hammer must be manually set, by either thumbing it back as one would on a revolver, or cycling the slide, which in turn rides over the hammer and sets it. However, after that first shot, the difference between a single action revolver and a single action semi-automatic is apparent, as the slide’s rearward movement serves to cock the hammer for each subsequent shot, rather than on a revolver where it must be manually thumbed back every time.
Of course, just as Robert Adams realized with the revolver, it didn’t take gunmakers long to come to the conclusion that there was a market for a semi-automatic handgun that did away with the single action’s requirement of being cocked initially. Now typically referred to as a double action only pistol, or DAO, these semi-automatic pistols operate in a manner that’s utterly identical to that of their revolver-shaped brethren: the trigger both cocks, and releases the hammer, firing a round each time. Like the single action pistol, the DAO pistol’s slide does ride over the hammer, but unlike the single action pistol, the slide does not leave the hammer cocked when it returns to battery (“in battery” means ready to fire).
But of course, if you follow the logical train of thought that’s led to these various guns’ development, you now might be asking yourself “why hasn’t someone made a gun that doesn’t need to be cocked the first time, but uses the slide’s cycling to cock it for every subsequent shot?” Well, they have, and this is where the business of defining a gun as a double or single action gets murky. Known as double action/single action, or more commonly as DA/SA, these guns combine the double action semi-automatic’s operation with that of the single-action to produce a gun that, from an uncocked condition, can cock the hammer and release it with a single pull of the trigger, but is also cocked each time the slide cycles rearward. With the understanding that this results in a gun in which the first shot is fired by double-action operation, and each subsequent shot is fired in single-action, these gun’s DA/SA monikers actually begin to make sense.
Of course, deciding which one of these various actions is best is more a matter of examining your own personal needs, and cannot be done without the context of usage. DA/SA guns, for example, are often referred to as safer than their SA counterparts as they can be left uncocked, but are still ready to fire at a moment’s notice. However, the flip side is that the trigger feels and responds quite differently after the first shot on a DA/SA, as the single-action trigger is typically far lighter and shorter. This has all sort of ramifications to competitive shooters here in Canada, but is much more important to law enforcement officers and Americans who are considering a handgun for self-defence, hence the frequency with which the term DA/SA comes up in American handgun discussions. At the other end of the spectrum, people who love the meticulous and fine nature of a revolver might enjoy the manipulation of a single-action revolver, from the ritual involved in loading it to the motion of cocking it before each firing. In either case though, at least now you’ll know what they’re talking about when they start telling you how much they like their single-action guns over their double-actions!
The red-headed stepchild: Striker-fired actions
All this discussion of single-action and double-action pistols ignores one very large, and often polymer-based elephant in the room: the striker-fired pistol. The newest variation on the handgun theme, the striker-fired pistol (most famously and commonly represented by Glock’s handguns) trades a traditional hammer and firing pin assembly for a spring-loaded firing pin, or striker, that is released by the trigger and driven into the primer by a spring. By comparison, hammer-fired guns use firing pins that are either free floating or held to the rear (away from the chamber) by a light spring, and fired by the force of the hammer literally hammering the firing pin into the primer. However, the differences don’t end there.
While a hammer-fired handgun can rely on either the trigger or the slide to cock the action, a striker-fired gun requires the use of both. Cycling the slide to load the first round into the chamber sets the striker to what essentially amounts to a half-cock position. From this position, the squeezing of the trigger engages the striker and moves it out of this half-cocked position towards the rear of the gun, further compressing its spring and bringing the gun to full cock. At this point the trigger releases the striker, and its firing spring drives the striker forward, igniting the primer and launching a round downrange. As this happens, the slide unlocks, travels to the rear, and sets the striker to its familiar quasi-half cocked position.
The logic behind this is that striker-fired guns benefit from the traditional double-action’s ability to fire without needing to be cocked, but do so without the encumbrance of the heavy and long trigger pull often required to cock a hammer-fired gun. Additionally, they are reported to be safer, as the design of most striker fired guns is such that a striker released from the half-cock position will not have enough energy to ignite a primer, just as a trigger will not be capable of fully cocking the striker. But, since they rely on both the trigger and slide to account for half of the firing mechanism, they cannot be classified as single- or double-action pistols.